17.1 - 17.9 Inherited change Flashcards
Define genotype
The genetic makeup of an organism, all the alleles that an organism has.
Define phenotype
The observable or biochemical characteristic of an organism. Resulting from both the genotype and environental effects.
Define gene
Sections of DNA that code for the production of a specific polypeptide, found at a particular position on the DNA molecule called the locus.
Define allele
Different forms of the same gene. They code for slightly different polypeptides but are found at the same loci in diploid organisms with homologous pairs of chromosomes.
Define heterozygous
When the alleles on both chromosomes are different
Define homozygous
When the alleles on both chromosomes are the same
Define dominant
An allele which is always expressed if present
Define recessive
Only expressed if two copies of this allele are present
Define codominance
When two different alleles are both expressed in the phenotype
Define multiple alleles
If a gene has more than two forms of alleles
Define monohybrid inheritance
The inheritance of a single gene
What reasons are there for the observed phenotypic ratios of offspring not being the same as expected?
- Small sample size
- Fusion of gametes is random
- Linked genes
- Epistasis
- Lethal genotype
Define dihybrid inheritance
Two characteristcs, determined by two different genes located on different chromosomes
Define sex linkage
Any gene found on the x or y chromosome is said to be sex-linked
Because the x-chromosome is much longer than the y, some genes are found only on the x chromosome. The x chromosome has a non-homolgous portion that is not found on the y.
Define autosomal linkage
When two or more genes are carried on the same autosome, they will remain together during independent segregation. The closer the loci of the two genes, the less likely crossing over would seperate them.
